The overall hypothesis of Project #3 is that the accelerated atherogenesis associated with diabetes is due to decreased production, or decreased bioactivity of endothelial-derived NO. In aim #1 we will determine if diabetes accelerates atherogenesis in the thoracic aorta of diabetic rabbits fed an atherogenic diet by decreasing the production or bioactivity of NO. Lesion size by morphometry will be assessed at 5 and 10 weeks of hyperlipidemic diet. Bioactivity of NO will be measured by assessing endothelium- dependent and exogenous NO-induced relaxations and increases in cGMP in the two arteries. NO production will be assessed by chemiluminescence. To determine the role of NO, NO will be modulated in vivo by chronic administration of NO synthase inhibitors and NO donors. The role of increased oxidative stress in decreasing NO bioactivity will be determined by measuring superoxide anion production, determining the effect of superoxide anion scavengers, and treating rabbits with vitamin E and probucol. Lipid peroxidation and rabbit lipoprotein oxidation will be measured in collaboration with Project #1. The role of vasoconstrictor prostanoids will be evaluated by treating rabbits with indomethacin and a thromboxane A2 receptor antagonist. The influence of insulin and an aldose reductase inhibitor on atherogenesis and NO bioactivity will also be determined. In aim #2 we will determine if adhesion molecule expression and monocyte adhesion is increased in diabetic rabbits and in cultured endothelial cells exposed to elevated glucose as a result of decreased synthesis or bioactivity of NO. Adhesion of monocytes will be quantitated, and surface expression of adhesion molecules including VCAM-l, ICAM-I and ELAM-l, will be measured by a fluorescent tagged ELISA assay in cultured cells and in Hautchen preparations of the aorta. Alterations in NO synthesis by elevated glucose will be studied in collaboration with Project #2. Bioactivity of NO will be determined independently by changes in endothelial cGMP levels. In collaboration with Project #1 the combined influence of oxidized lipoproteins and hyperglycemia will be determined in cultured cells. The bioactivity of NO will be modulated with NO inhibitors and donors, and antioxidants. The proposed studies will be important to the program in producing an animal model in which to test the hypothesis that impaired NO function is related to accelerated atherosclerosis in diabetes.